Author Topic: Carbs overflow  (Read 1815 times)

Offline AndyD

  • SOHC Expert
  • Posts: 318
    • View Profile
Re: Carbs overflow
« Reply #15 on: June 21, 2020, 06:43:29 PM »
Had another play with the carbs on the bench today and tried the original valve seats / needles but these let pressure drop significantly quicker than the Keyster ones despite repeated cleaning and polishing etc.
One thing I did notice was that without the bottom bowl, the floats could occasionally stick open when turned over and then drop down with any movement. Nothing seems to be rubbing or catching and I think the spring thingy in the bottom bowl would also limit how far the floats can drop when fitted.
I plugged in the float height gauges I made up for the GS1000 a while ago to see if this could shed any light on the problem and they certainly help see what's happening.
Sure enough as soon as fuel is turned on the carbs fill and then overflow at a quick rate.
Turned the fuel off, gave the whole assembly a good shake and when turned back on the fuel level stayed at the right level.
Left them for an hour or so and no leaks.
Drained them and then turned fuel on and once again the levels go too high and overflow. And again, turning off the fuel and shaking them stops the leaking.
So it looks like for some reason the floats on initial filling don't shut off the supply but once they are 'encouraged' with a shake they work fine.
Floats and pins etc. all look fine and move very easily so I can't see any reason for this behaviour so may play a bit more on the bench before wrestling with the airbox etc. to put on the bike again.
Cheers,
Andy

Offline Bryanj

  • Grogu
  • *
  • Posts: 10692
    • View Profile
Re: Carbs overflow
« Reply #16 on: June 21, 2020, 07:13:08 PM »
Slightest bid of crud or roughness on the pivot pin or iside the pivot tube can cause all sorts of troubles

Offline AndyD

  • SOHC Expert
  • Posts: 318
    • View Profile
Re: Carbs overflow
« Reply #17 on: June 22, 2020, 09:22:04 AM »
Thanks Bryan,
I'll pop the bowls off one last time and give the pivots a final check / clean then I think I'll try them on the bike and keep fingers crossed.

Cheers,
Andy

Offline DaveN

  • Newbie
  • Posts: 47
  • 'You don't buy beer, son, you just rent it"
    • View Profile
Re: Carbs overflow
« Reply #18 on: June 22, 2020, 05:39:56 PM »
Does anyone know if you can buy replacement pivot pins?

One of mine has been mangled and is shorter than the others.
1977 Honda CB400F Super Sport
2016 Herald Classic 250
*1979 Honda CB550K*
*1980 Honda C90*
*1973 Suzuki GT185*
*1968 BSA Bantam Bushman*
*1964 NSU Quickly*

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Carbs overflow
« Reply #19 on: June 22, 2020, 05:45:05 PM »
Does anyone know if you can buy replacement pivot pins?

One of mine has been mangled and is shorter than the others.
Buy a length of brass rod of the correct size, model makers use it a lot, and make your own, it works out very, very cheap. On ebay, just type in brass rod. Here is the item number 133013228554

[ Guests cannot view attachments ]
« Last Edit: June 22, 2020, 05:48:51 PM by Nurse Julie »
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Bryanj

  • Grogu
  • *
  • Posts: 10692
    • View Profile
Re: Carbs overflow
« Reply #20 on: June 22, 2020, 05:54:41 PM »
Only comes with the float in new parts lists but old 500 parts book says 16126-259-004 for just pin.
May have an old one somewhere you can have cheap.

EDIT
DS sez 2 weeks so probably from his US warehouse
« Last Edit: June 22, 2020, 05:59:01 PM by Bryanj »

Offline Moorey

  • SOHC Master
  • Posts: 1666
    • View Profile
Re: Carbs overflow
« Reply #21 on: June 22, 2020, 06:40:27 PM »
Don't forget to carry a tapping stick for the float bowls.   ;)

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Carbs overflow
« Reply #22 on: June 22, 2020, 07:12:29 PM »
Does anyone know if you can buy replacement pivot pins?

One of mine has been mangled and is shorter than the others.
Buy a length of brass rod of the correct size, model makers use it a lot, and make your own, it works out very, very cheap. On ebay, just type in brass rod. Here is the item number 133013228554

(Attachment Link)

To save me measuring what the pivot pins are can you let us all know what size is required?
Indeed I will Ken, as soon as I have cooked dinner 😁😁😁
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Carbs overflow
« Reply #23 on: June 22, 2020, 09:36:43 PM »
2mm. That's the size of the brass rod to buy if you want to make your own float pins.
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline DaveN

  • Newbie
  • Posts: 47
  • 'You don't buy beer, son, you just rent it"
    • View Profile
« Last Edit: June 23, 2020, 12:05:53 PM by DaveN »
1977 Honda CB400F Super Sport
2016 Herald Classic 250
*1979 Honda CB550K*
*1980 Honda C90*
*1973 Suzuki GT185*
*1968 BSA Bantam Bushman*
*1964 NSU Quickly*

Offline DaveN

  • Newbie
  • Posts: 47
  • 'You don't buy beer, son, you just rent it"
    • View Profile
Re: Carbs overflow
« Reply #25 on: July 04, 2020, 11:00:11 PM »
All done!
Carbs off and cleaned up in a sonic bath courtesy of my neighbour Steve.

I think I may of found the issue with the sticking floats - one float pivot pin had the end sheared off and another was bent as a dog's back leg!

[ Guests cannot view attachments ]

Bought a set of the brass rods off of Amazon and cut new pins for all 4 carbs, float levels checked and matched and back on the bike this afternoon and runs like a dream with no overflow  ;D
1977 Honda CB400F Super Sport
2016 Herald Classic 250
*1979 Honda CB550K*
*1980 Honda C90*
*1973 Suzuki GT185*
*1968 BSA Bantam Bushman*
*1964 NSU Quickly*

Offline DaveN

  • Newbie
  • Posts: 47
  • 'You don't buy beer, son, you just rent it"
    • View Profile
Re: Carbs overflow
« Reply #26 on: July 15, 2020, 11:18:27 PM »
If anybody needs some pins, I have a few  ;D
1977 Honda CB400F Super Sport
2016 Herald Classic 250
*1979 Honda CB550K*
*1980 Honda C90*
*1973 Suzuki GT185*
*1968 BSA Bantam Bushman*
*1964 NSU Quickly*

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal